The present invention relates to the control of glass melting furnaces for the purpose of automating their operation, including during transient phases, of improving the quality of the glass produced and of reducing the consumption of fuels as well as the amount of pollutants that are discharged. This invention may be applied to any type of glass melting and/or refining furnace, namely firing, end-fired or cross-fired, electric or mixed (flame+electric) furnaces, and to any type of glass produced.
The present invention therefore aims to provide a device for controlling the melting of the glass batch, of the fuzzy control type, designed so as to automatically carry out all or some of the set of operations for controlling the operating parameters of the furnace as well as all or some of the set of operations for operating the actuators which control the equipment of the furnace, on the basis of the strategies that an operator carrying out these operations manually would employ.
It is known that the control of a glass furnace is a particularly tricky and complicated operation, especially because of the very large number of parameters involved in controlling the furnace and the considerable inertia of these furnaces, as well as the very slow variation in the parameters and phenomena involved in controlling the melting of the glass.
It follows that the control of glass furnaces often remains empirical, being generally limited to adjustment of the furnace crown temperatures by acting manually on control devices which act on the actuators which control heating and cooling equipment of the furnace and on the equipment for feeding it with the glass batch. These actions generally rely on the experience of the operator as well as on his analysis of how the furnace and the melt hat it contains are behaving, in particular his visual estimation of the conditions in which the melting and/or refining of the glass composition inside the furnace is/are taking place.
It follows from this empiricism that the principle on which to make decisions about actions to be taken with regard to a given situation in the furnace is difficult to formalize.
To solve this problem, operators generally draw up tables giving the status of all the measurable parameters of the furnace, in a given production configuration, so as to try to reproduce these parameters in a similar production situation. The number of parameters involved and she lack of knowledge about their relationship or interactions make this operation complicated during steady operation of the furnace. It is even more difficult during transient phases, such as a change of production or a change of colour, or example. Thus it may be imagined that a glass furnace can only be controlled by skilled operators with a great deal of experience.
The decisions taken therefore often depend on the experience or common practices of each operator and it follows that any generalization of the furnace control principles is extremely difficult. The operators, in their control of the furnace, work to within a safety factor with respect to the optimum operating conditions so as not to risk degrading the quality of the glass, this procedure limiting the efficiency or performance of the furnace.
The manual mode of controlling the glass furnace proves even more limited when managing the transient phases which correspond to changes in tonnage of the furnace or to changes in the type or color of the glass, or other such changes.
Reference will now be made to FIG. 1 of the appended drawings, which shows, diagrammatically, in perspective and with partial cut-away, one embodiment of a glass melting furnace to which the present invention may be applied.
This furnace, in a known manner, mainly consists of a tank 1, made of refractory materials, in which the glass 2 is melted. This tank has side walls 3 made of refractory materials and a crown 4. The chamber of the furnace is heated using burners 5 which are set in at least one of the walls of the furnace.
The melted and refined glass is temperature-conditioned, in a zone of the furnace generally called a working chamber 6, and is then delivered to the forming equipment represented schematically by the reference 7, which may be of any known type, especially machines for forming hollow glassware (bottles) or equipment for forming glass sheet for the purpose of obtaining flat glass (window glass).
The glass batch is introduced into the furnace via one or more devices of the batch charger 8 type, which are set into one or more of the walls of the furnace, these devices depositing and pushing the glass batch on the surface of the molten glass, in the form or independent batch piles or of a blanket 9 of defined composition.
The walls 3 of the furnace furthermore include a number of openings (not shown in the drawing) so as to allow the operators to observe the melting of the glass in the furnace chamber, the shape of the burner flames, the spreading of the batch on the surface of the glass melt, the operation of the bubblers, etc.
The furnace furthermore includes a number of sensors and detection means for measuring the operating parameters of the furnace and of its peripheral equipment, such as the working chamber 6, the fuel and oxidizer circuits, the fume circuits, the cooling circuits, all the fluid circuits, as well as the positions of the actuators (control valves, devices for varying the electrical power, etc.), position-control members, and other such devices. The values thus measured correspond to each space of the observed quantity or parameter (temperatures, flow rates, pressures, speeds, positions, etc.).
Starting from this state of the art, the present invention is intended to provide a device for monitoring and controlling the melting and/or refining of the glass batch in a glass melting furnace, which automatically carries out all or some of the set of operations for controlling the operating parameters of the furnace as well as all or some of the set of operations for operating the actuators of the furnace, on the basis of the strategies that an operator carrying out these operations manually would employ. The device forming the subject of the present invention is characterized in that it comprises:
an analysis and control device, of the fuzzy-controller type, using a control algorithm of the fuzzy-logic type which receives all the information relating to the operation of the furnace coming from the sensors and from the detection means provided on this furnace, as well as the set point values input manually by the operators, this control algorithm delivering control signals to the various actuators and control means of the furnace and,
a predictive system, of the neural- and/or fuzzy-type, which, depending on the initial state of the furnace and of its parameters and on the modification of at least one of the said parameters, determines the predicted change over time of the state of the furnace and of its parameters, this predicted change in the state of the furnace being used as input data for the fuzzy controller which determines the new set point values for the furnace actuators which are necessary for maintaining optimum operation of the furnace compatible with the defined objectives.
This predicted change in the state of the furnace and of its parameters forms part of the input data for the controller of the fuzzy-logic type which will determine the set points that have to be applied to the various actuators for operating and controlling the equipment of the furnace so as to maintain the objectives defined by the operator, such as, for example, the crown temperatures or the quality of the glass produced.
According to a second embodiment of the control device forming the subject of the present invention, this device furthermore includes a learning or computing device which is used during the learning phase of the neural- and/or fuzzy-type predictive system, i.e. during the phase of acquisition or the operating laws of the furnace. According to the invention, this learning, determining or computing device uses a computer model of the numerical-model type making it possible to define the laws governing the operation of the furnace, either from the learning phase of this predictive system, on the actual furnace, or by simulating the operation of the furnace using a mathematical model.
According to a preferred embodiment of the device forming the subject of the invention, this device furthermore includes a means for the acquisition and processing of the image of the inside of the furnace, operating in the visible, infrared or other spectrum, the means possibly consisting of a system of video cameras positioned in the furnace in order to observer zones corresponding to a phenomenon relating to the melting and/or to the refining of the glass, the images thus obtained then being processed so as to obtain information relating to the observed phenomenon, this information being shaped for the purpose of being introduced as input data for the furnace control algorithm so as to monitor and control the observed phenomenon.
Other features and advantages of the present invention will emerge from the description given below with reference to the appended drawing which illustrates one embodiment thereof, given by way or example and devoid of any limiting character.